@Ioigor 

Theoretically, the different hardware version of Deco P7 are compatible with each other. 

Is there any error message that indicates the new Deco P7 cannot be recognized? 

You can turn on the main Deco only and connect the new Deco to the main one by wired cable directly and ensure that the led is flashing blue.

Or you can swap different new Deco to add first.

May it work and have a good day. 

@Kevin_Z 

I try all walkthrough from your site.
Deco P7 V1.0 work great alone, also P7 V1.1.
When I try to put together in the same wi-fi network app never found a new P7.

@Ioigor 

Thanks for your reply.

May I know which step you get stuck when you add the new slave Deco P7？ You can show us a screenshot of it. 

If the new Deco P7 cannot be found on the Deco app, have you ever tried  to connect the slave Deco to the main Deco by wired cable to add it? 

Besides, you can try to reinstall the Deco app or change another smart phone to give it a go.

Any updates, please let us know.

May it help and have a good day.